The present invention is related to the field of patient monitoring equipment.
Patient monitoring systems are used in many settings to assist medical personnel in providing care. In many settings, such as hospital wards and nursing homes, there can be problems associated with patients' getting out of bed without supervision or assistance. A patient may suffer a fall whose effects can range from minor to major. Older patients are at risk of breaking their hips in a fall, requiring extended bed rest and attendant problems. Systems have been known that monitor whether a patient is present in a bed or wheelchair. Essentially, these systems employ a flat sensor laid on the mattress or cushion, and electronic apparatus that responds to signals from the sensor. For example, the strength of a sensor output signal may be proportional to the weight applied to the sensor. The electronic apparatus therefore compares the sensor output signal with one or more predetermined values corresponding to significant thresholds of interest. For example, if the sensor output signal falls below a predetermined low value, the apparatus generates an indication that the patient has gotten out of bed.
Prior patient monitoring systems have used sensors having certain drawbacks that limit performance. One such drawback is size. Sensors to be used on a bed are as wide as the bed, but extend only about a foot in the longitudinal direction. These sensors are intended for placement in the middle of the bed, on the assumption that a patient's weight is concentrated there. However, a patient may move into a position away from the sensor, resulting in a false alarm. Existing sensors have also employed switches as sensing elements, which can provide only a binary indication. Due to the lack of resolution, only limited information can be obtained from the sensor.